Middle of the line (MOL) contacts with two-dimensional self-alignment

ABSTRACT

Disclosed are methods of forming an integrated circuit (IC) structure with self-aligned middle of the line (MOL) contacts and the resulting IC structure. In the methods, different, selectively etchable, dielectric materials are used above the gate level for: a dielectric cap above a gate; a dielectric spacer above a gate sidewall spacer and laterally surrounding the dielectric cap; and a stack of dielectric layer(s) that covers the dielectric cap, the dielectric spacer, and metal plugs positioned laterally adjacent to the dielectric spacer and above source/drain regions. Due to the different dielectric materials, subsequently formed gate and source/drain contacts are self-aligned in two dimensions to provide protection against the occurrence of opens between wires and/or vias in the first BEOL metal level and the contacts and to further provide protection against the occurrence of shorts between the gate contact and any metal plugs and between the source/drain contacts and the gate.

FIELD OF THE INVENTION

The present invention relates to the middle of the line (MOL) contactsthat connect field effect transistors (FETs) to back end of the line(BEOL) metal levels. More particularly, the present invention relates tointegrated circuit (IC) structures and methods of forming these ICstructures so as to have MOL contacts (e.g., gate and source/draincontacts) with two-dimensional self-alignment and, thus, so that gatecontact(s) can, optionally, be formed within an active region of a FET(or close thereto).

BACKGROUND

Integrated circuit (IC) structures have middle of the line (MOL)contacts that connect field effect transistors (FETs) to back end of theline (BEOL) metal levels. The MOL contacts include at least one gatecontact (also referred to herein as a CB contact) and source/draincontacts (also referred to herein as CA contacts). Each gate contactextends vertically through the interlayer dielectric (ILD) material froma metal wire or via in the first BEOL metal level (also referred toherein as the M₀ level) to the gate of the FET. Each source/draincontact extends vertically through the ILD material from a metal wire orvia in the first BEOL metal level to a metal plug (also referred toherein as a TS contact), which is above and immediately adjacent to asource/drain region of the FET. Conventional techniques for formingthese MOL contacts inherently include risks of the following: (a) opens(also referred to herein as voids) occurring between the first BEOLmetal level and both the source/drain contacts and the gate contact; (b)shorts occurring between the gate contact and a metal plug,particularly, if the gate contact is to be formed on a portion of thegate above the active region of the FET (i.e., particularly, if the gatecontact is a gate contact over active, also referred to herein as aCBoA) in order to allow for size scaling; and (c) shorts occurringbetween the source/drain contacts and the gate. Thus, there is a need inthe art for an improved method of forming an IC structure with MOLcontacts in a manner that avoids the occurrence of the above-describedopens and shorts.

SUMMARY

In view of the foregoing, disclosed herein are methods of forming anintegrated circuit (IC) structure with self-aligned middle of the line(MOL) contacts. Generally, these methods include forming at least onefield effect transistor (FET). The FET can be formed so as to have asemiconductor body and, in the semiconductor body, source/drain regionsand a channel region positioned laterally between the source/drainregions. The FET can further be formed so as to have a gate with a gatesidewall spacer above the semiconductor body at the channel region. Adielectric spacer can be formed above the gate sidewall spacer. Adielectric cap can be formed above the gate so as to be laterallysurrounded by and immediately adjacent to the dielectric spacer.Additionally, metal plugs can be formed above the semiconductor body atthe source/drain regions such that the metal plugs are positionedlaterally adjacent to the dielectric spacer opposite the dielectric cap.

To complete the IC structure, both middle of the line (MOL) contacts andback end of the line (BEOL) metal levels can be formed. Specifically, atleast one dielectric layer can be formed over the dielectric cap, thedielectric spacer and the metal plugs. Trenches can be formed in anupper portion of the dielectric layer(s) and contact openings can beformed that extend from the trenches through a lower portion of thedielectric layer(s). The contact openings can include, but are notlimited to, a first contact opening that extends from a first trenchthrough the lower portion of the dielectric layer(s) and the dielectriccap to the gate and a second contact opening that extends from a secondtrench through the lower portion of the dielectric layer(s) to a metalplug. After the trenches and contact openings are formed, metal can bedeposited to form wires in the trenches and contacts in the contactopenings (e.g., a first contact to the gate in the first contact openingand a second contact to a metal plug in the second contact opening). Itshould be noted, in these methods, the dielectric cap, the dielectricspacer, and the dielectric layer(s) are specifically made of differentdielectric materials such that the first contact and second contact areeach self-aligned (e.g., in two different dimensions).

The IC structures formed according to these methods can include, but arenot limited to, IC structures that incorporate planar FET(s) ornon-planar FET(s), IC structures that incorporate FET(s) with multiplesemiconductor bodies, IC structures that incorporate FET(s) withconventional gate-first gate(s) or replacement metal gate(s), etc.

Thus, for example, one particular method embodiment disclosed herein canbe used to form an IC structure with self-aligned MOL contacts tomultiple non-planar FETs. This particular method embodiment can includeforming the non-planar FETs. To form the FETs, multiple semiconductorbody can be formed. Each semiconductor body can have multiple channelregions, each channel region positioned laterally between source/drainregions. Sacrificial gates with gate sidewall spacers can be formed onthe semiconductor bodies adjacent to the channel regions. Raisedsource/drain regions can be formed on the semiconductor bodies at thesource/drain regions such that the raised source/drain regions arepositioned laterally adjacent to the gate sidewall spacers. A firstinterlayer dielectric (ILD) layer can be formed so as to cover thesacrificial gates, the gate sidewall spacers and the raised source/drainregions. After the first ILD layer is formed, it can be planarized toexpose the tops of the sacrificial gates and gate sidewall spacers andthe sacrificial gates can be replaced with replacement metal gates.

The replacement metal gates and the gate sidewall spacers cansubsequently be recessed and dielectric spacers can be formed on exposedvertical surfaces of the first ILD layer above each gate sidewallspacer. Next, dielectric caps can be formed on the replacement metalgates such that each dielectric cap is laterally surrounded by andimmediately adjacent to a dielectric spacer. Additionally, metal plugopenings, which extend through the first ILD layer to the raisedsource/drain regions, can be formed. Metal plugs can be formed in themetal plug openings and then recessed, thereby forming recessed metalplugs.

To complete the IC structure, both middle of the line (MOL) contacts andback end of the line (BEOL) metal levels can be formed. Specifically, astack of dielectric layers can be deposited over the dielectric caps,the dielectric spacers, and the recessed metal plugs. This stack ofdielectric layers can include a second ILD layer and a hardmask layer onthe second ILD layer. Trenches can be formed in an upper portion of thestack and contact openings can be formed that extend from the trenchesthrough a lower portion of the stack. The contact openings can include,but are not limited to, a first contact opening that extends from afirst trench through the lower portion of the stack and through adielectric cap to a replacement metal gate and a second contact openingthat extends from a second trench through the lower portion of the stackto a metal plug. After the trenches and contact openings are formed,metal can be deposited to form wires in the trenches and contacts in thecontact openings (e.g., a first contact to the replacement metal gate inthe first contact opening and a second contact to the metal plug in thesecond contact opening). In this method embodiment, the dielectric caps,the dielectric spacers, and each of the dielectric layers in the stackare specifically made of different dielectric materials so that thefirst contact and second contact will be self-aligned in two differentdimensions.

Also disclosed herein are integrated circuit (IC) structures formedaccording to the methods described above. Generally, each IC structureincludes at least one field effect transistor (FET). The FET can have atleast one semiconductor body and, in the semiconductor body, a channelregion positioned laterally between source/drain regions. A gate can beabove the semiconductor body at the channel region. A gate sidewallspacer can be on the sidewalls of the gate, a dielectric cap can be on atop surface of the gate, and a dielectric spacer can be above the gatesidewall spacer so as to laterally surround and be immediately adjacentto the dielectric cap. Metal plugs can be above the source/drain regionsand positioned laterally adjacent to the dielectric spacer.

Each IC structure can further have both middle of the line (MOL)contacts and back end of the line (BEOL) metal levels. That is, at leastone dielectric layer can be above the dielectric cap, the dielectricspacer and the metal plugs. Wires can be in an upper portion of the atleast one dielectric layer and contacts can extend from the wiresthrough a lower portion of the at least one dielectric layer. Thesecontacts can include, but are not limited to, a first contact thatextends from a first wire through the lower portion of the at least onedielectric layer and through the dielectric cap to the gate and a secondcontact that extends from a second wire through the lower portion of theat least one dielectric layer to a metal plug. It should be noted that,in the IC structures, the dielectric cap, the dielectric spacer, and theat least one dielectric layer are all specifically made of differentdielectric materials such that the first contact and the second contactare each self-aligned (e.g., in two different dimensions).

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention will be better understood from the followingdetailed description with reference to the drawings, which are notnecessarily drawn to scale and in which:

FIG. 1 is a flow diagram illustrating methods of forming an integratedcircuit (IC) structure with self-aligned middle of the line (MOL)contacts to at least one field effect transistor (FET);

FIGS. 2A-2B are top view and cross-section diagrams, respectively,illustrating a partially completed structure formed according to themethods of FIG. 1;

FIG. 3 is a top view diagram illustrating a partially completedstructure formed according to the methods of FIG. 1;

FIG. 4 is a top view diagram illustrating a partially completedstructure formed according to the methods of FIG. 1;

FIG. 5A is a top view diagram and FIGS. 5B-5D are differentcross-section diagrams illustrating a partially completed structureformed according to the methods of FIG. 1;

FIG. 6A is a top view diagram and FIGS. 6B-6C are differentcross-section diagrams illustrating a partially completed structureformed according to the methods of FIG. 1;

FIG. 7A is a top view diagram and FIGS. 7B-7C are differentcross-section diagrams illustrating a partially completed structureformed according to the methods of FIG. 1;

FIG. 8A is a top view diagram and FIGS. 8B-8C are differentcross-section diagrams illustrating a partially completed structureformed according to the methods of FIG. 1;

FIG. 9A is a top view diagram and FIGS. 9B-9C are differentcross-section diagrams illustrating a partially completed structureformed according to the methods of FIG. 1;

FIG. 10A is a top view diagram and FIGS. 10B-10C are differentcross-section diagrams illustrating a partially completed structureformed according to the methods of FIG. 1;

FIG. 11A is a top view diagram and FIGS. 11B-11C are differentcross-section diagrams illustrating a partially completed structureformed according to the methods of FIG. 1;

FIG. 12A is a top view diagram and FIGS. 12B-12E are differentcross-section diagrams illustrating a partially completed structureformed according to the methods of FIG. 1;

FIG. 13A is a top view diagram and FIGS. 13B-13C are differentcross-section diagrams illustrating a partially completed structureformed according to the methods of FIG. 1;

FIG. 14A is a top view diagram and FIGS. 14B-14C are differentcross-section diagrams illustrating a partially completed structureformed according to the methods of FIG. 1; and

FIGS. 15A-15D are different cross-section diagrams illustratingcompleted structure formed according to the methods of FIG. 1.

DETAILED DESCRIPTION

As mentioned above, integrated circuit (IC) structures have middle ofthe line (MOL) contacts that connect field effect transistors (FETs) toback end of the line (BEOL) metal levels. The MOL contacts include atleast one gate contact (also referred to herein as a CB contact) andsource/drain contacts (also referred to herein as CA contacts). Eachgate contact extends vertically through the interlayer dielectric (ILD)material from a metal wire or via in the first BEOL metal level (alsoreferred to herein as the M0 level) to the gate of the FET. Eachsource/drain contact extends vertically through the ILD material from ametal wire or via in the first BEOL metal level to a metal plug (alsoreferred to herein as a TS contact), which is above and immediatelyadjacent to a source/drain region of the FET. Conventional techniquesfor forming these MOL contacts inherently include risks of thefollowing: (a) opens (also referred to herein as voids) occurringbetween the first BEOL metal level and both the source/drain contactsand the gate contact; (b) shorts occurring between the gate contact anda metal plug, particularly, if the gate contact is to be formed on aportion of the gate above the active region of the FET (i.e.,particularly, if the gate contact is a gate contact over active, alsoreferred to herein as a CBoA) in order to allow for size scaling; and(c) shorts occurring between the source/drain contacts and the gate.

In view of the foregoing, disclosed herein are methods of forming anintegrated circuit (IC) structure with self-aligned middle of the line(MOL) contacts to at least one field effect transistor (FET). In themethods, different, selectively etchable, dielectric materials are usedabove the gate level for at least the following: a dielectric cap abovea gate; a dielectric spacer above a gate sidewall spacer and laterallysurrounding the dielectric cap; and at least one dielectric layer thatcovers the dielectric cap, the dielectric spacer, and metal plugspositioned laterally adjacent to the dielectric spacer and abovesource/drain regions. Due to the different dielectric materials usedabove the gate level, subsequently formed gate and source/drain contactswill be self-aligned (e.g., in two different dimensions) to provideprotection against the occurrence of opens between wires and/or vias inthe first BEOL metal level and the various contacts and to furtherprovide protection against the occurrence of shorts between the gatecontact and any metal plugs and between the source/drain contacts andthe gate. Also disclosed herein are IC structures formed according tothe methods.

Referring to the flow diagram of FIG. 1, generally in the methodsdisclosed herein a semiconductor wafer is provided (101) and at leastone field effect transistor (FET) can be formed on the semiconductorwafer (102). Each FET can be formed so that it has one or moresemiconductor bodies. Each semiconductor body can be a planarsemiconductor body for a planar FET or a non-planar semiconductor body(e.g., a semiconductor fin) for a non-planar FET, such as a fin-type FET(finFET) or a trigate FET. In any case, each semiconductor body can haveareas designated for source/drain regions and for a channel regionpositioned laterally between the source/drain regions. The FET canfurther be formed so that it has a gate adjacent to the channel region(or channel regions in the case of multiple semiconductor bodies), agate sidewall spacer adjacent to the gate and a first interlayerdielectric (ILD) layer positioned laterally immediately adjacent to thegate sidewall spacer and above the source/drain regions. The gate can bea conventional gate-first gate (e.g., a gate with a silicon dioxide gatedielectric layer and a polysilicon gate conductor layer or any othersuitable gate-first gate configuration). Alternatively, this gate can bea replacement metal gate (e.g., a gate with a high-K gate dielectriclayer and a metal gate conductor layer or any other suitable replacementmetal gate configuration) formed by removing a previously formedsacrificial gate and replacing that sacrificial gate with a metal gate(as discussed in greater detail below). In any case, those skilled inthe art will recognize that, in the case of a planar FET, the gate willbe positioned adjacent to the top surface of each semiconductor body atthe channel region, whereas, in the case of a non-planar FET, the gatewill be positioned adjacent to opposing sidewalls and, optionally, abovethe top surface of each semiconductor body at the channel region.

In the methods described herein, the gate and the gate sidewall spacercan be recessed to expose vertical surfaces of the first ILD layer(104), a dielectric spacer can be formed on the exposed verticalsurfaces of the first ILD layer above the gate sidewall spacer (106),and a dielectric cap can be formed above the gate such that it islaterally surrounded by and immediately adjacent to the dielectricspacer (108). Additionally, metal plugs can be formed within the firstILD layer above the source/drain regions such that the dielectric spaceris positioned laterally between each metal plug and the dielectric cap(110). After the metal plugs are formed, they too can be recessed toform recessed metal plugs and to expose additional vertical surfaces ofthe first ILD layer.

To complete the IC structure, both middle of the line (MOL) contacts andback end of the line (BEOL) metal levels can be formed. Specifically, atleast one dielectric layer (e.g., a stack of dielectric layers includinga second ILD layer and a hardmask layer on the second ILD layer) can beformed over the dielectric cap, the dielectric spacer and the recessedmetal plugs (114). Trenches can then be formed in an upper portion ofthe dielectric layer(s) (116) and contact openings can be formed thatextend from the trenches through a lower portion of the dielectriclayer(s) (118). The contact openings can include, but are not limitedto, a first contact opening that extends from a first trench through thelower portion of the dielectric layer(s) and through the dielectric capto the gate (e.g., aligned above an active region of the FET or closethereto) (119) and a second contact opening that extends from a secondtrench through the lower portion of the dielectric layer(s) to a metalplug (120). After the trenches and contact openings are formed, metalcan be deposited to form wires in the trenches and contacts in thecontact openings (e.g., a first contact to the gate in the first contactopening and a second contact to a metal plug in the second contactopening) (122).

It should be noted that, at process 106-114 described above, thedielectric cap, the dielectric spacer, and the dielectric layer(s) arespecifically made of different dielectric materials such that variousselective etch processes can be used at process 118 to form the contactopenings. As a result, the contacts, including the first contact and thesecond contact, will each be self-aligned (e.g., in two differentdimensions), as discussed in greater detail below with regard to aparticular method embodiment and illustrated in the Figures. Thoseskilled in the art will recognize that, due to the self-alignment of thecontacts and, particularly, the self-alignment of the first contact tothe gate, the first contact can be formed so that it lands on the gateabove the active region of the FET (or close thereto) as opposed toabove adjacent isolation material without risking the occurrence of ashort between the first contact and any metal plugs. Thus, the methodsallow for device size scaling.

The IC structures formed according to the disclosed methods can include,but are not limited to, IC structures that incorporate planar FET(s) ornon-planar FET(s), IC structures that incorporate FET(s) with multiplesemiconductor bodies, IC structures that incorporate FET(s) withconventional gate-first gate(s) or a replacement metal gate(s), etc.Thus, for purposes of illustration, the method steps 101-122 aredescribed in greater detail below with reference to the formation of anIC structure with self-aligned MOL contacts to multiple non-planar FETs(e.g., multiple finFETs).

Referring again to the flow diagram of FIG. 1, this method embodimentcan include providing a semiconductor wafer (101) and forming multiplenon-planar FETs on the semiconductor wafer (102).

The semiconductor wafer provided at process 101 can be, for example, asemiconductor-on-insulator (SOI) wafer, as shown in FIG. 2B, thatincludes a semiconductor substrate 202 (e.g., a silicon substrate), aninsulator layer 203 (e.g., a buried oxide (BOX) layer or other suitableinsulator layer on the semiconductor substrate) and a semiconductorlayer (e.g., a silicon layer or other suitable semiconductor layer) onthe insulator layer 203. Alternatively, a bulk semiconductor wafer(e.g., a bulk silicon wafer or other suitable bulk semiconductor wafer)could be used.

Multiple semiconductor bodies 210 can be formed at process 102 such thateach semiconductor body has areas designated for multiple channelregions 211 with each channel region being positioned laterally betweena pair of source/drain regions 212. For purposes of illustration, FIGS.2A-2B show a pair of semiconductor bodies 210, wherein eachsemiconductor body has a first channel region and a second channelregion separated by a shared source/drain region. In any case, eachsemiconductor body 210 can be a fin-shaped semiconductor body (i.e.,relatively thin rectangular semiconductor body). Fin-shapedsemiconductor bodies can be patterned and etched from the semiconductorlayer of the SOI wafer (or, alternatively, from the upper portion of abulk semiconductor substrate, when isolation from the lower portion ofthe bulk semiconductor substrate is provided by buried well regions).Techniques for forming such fin-shaped semiconductor bodies (e.g.,lithographic patterning techniques or sidewall image transfertechniques) are well known in the art and, thus, the details have beenomitted from this specification in order to allow the reader to focus onthe salient aspects of the disclosed method. It should be noted that thesemiconductor bodies can be appropriately doped with a first dopant,either before or after formation, so that the channel regions 211 willhave a first-type conductivity at a relatively low conductivity level.

At process 102, replacement metal gates with gate sidewall spacers canbe formed across the semiconductor bodies 210 such that each replacementmetal gate with a gate sidewall spacer is positioned above the topsurfaces and adjacent to the opposing sides of the semiconductor bodiesat adjacent channel regions 211 (104). To form the replacement metalgates at process 104, a blanket first sacrificial layer (e.g., asacrificial polysilicon layer, a sacrificial amorphous silicon layer orother suitable sacrificial layer) can be formed above and adjacent tothe opposing sides of each semiconductor body 210. A second sacrificiallayer (e.g., a sacrificial nitride layer), which is different from thefirst sacrificial layer, can be formed on the top surface of the firstsacrificial layer. The first and second sacrificial layers can then bepatterned and etched to form sacrificial gates 231 (also referred toherein as dummy gates), wherein each sacrificial gate 231 is positionedabove the top surfaces and adjacent to the opposing sides of thesemiconductor bodies at adjacent channel regions and wherein eachsacrificial gate 231 has a sacrificial cap 232 (see FIGS. 2A-2B).

Next, gate sidewall spacers 240 can be formed on the sidewalls of thesacrificial gates 231 (see FIG. 3). That is, a relatively thin conformaldielectric layer (e.g., a silicon nitride layer, a silicon carbonnitride layer, a silicon boron carbon nitride layer or other suitableconformal dielectric layer) can be deposited over the partiallycompleted structure. Then, a directional etch process can be performedso as to remove the conformal dielectric layer from horizontal surfacesand from the sidewalls of the semiconductor bodies 210 at thesource/drain regions 212. Those skilled in the art will recognize thatthe height of the sacrificial cap 232 on the sacrificial gates 231should be approximately equal to or greater than the height of thesemiconductor bodies 210 so that the conformal dielectric layer can beremoved from the sidewalls of the semiconductor bodies 210 at thesource/drain regions 212 without exposing the sidewalls of thesacrificial gates 231.

A dopant implantation process can subsequently be performed to dope thesource/drain regions 212 with a second dopant so that the source/drainregions 212 have a second-type conductivity at a relatively highconductivity level. Additionally or alternatively, epitaxialsemiconductor material (e.g., epitaxial silicon or any other suitableepitaxial semiconductor material) can be deposited on exposed portionsof the semiconductor bodies 210 (i.e., on the source/drain regions 212)to form raised source/drain regions 213 (see FIG. 4). The epitaxialsemiconductor material can be in-situ doped or subsequently implantedwith the second dopant so that the source/drain regions 212 and theraised source/drain regions 213 have the second-type conductivity at therelatively high conductivity level. Optionally, before depositing theepitaxial semiconductor material, as described above, the source/drainregions 212 can be recessed (not shown), thereby ensuring that thesource/drain regions 212 and the epitaxial source/drain regions 213 willbe properly doped. If present, each raised source/drain region 213 willbe positioned laterally immediately adjacent to at least one gatesidewall spacer 240 opposite a sacrificial gate 231 and, optionally, theepitaxial semiconductor material on adjacent source/drain regions 212will be merged into a single region, as illustrated.

Next, a first interlayer dielectric (ILD) layer 250 can be formed overthe partially completed structure and then planarized (see FIGS. 5A-5D).Specifically, a blanket first ILD dielectric layer 250 (e.g., a blanketsilicon oxide layer or other suitable blanket ILD layer) can bedeposited so as to cover the sacrificial caps 232 and gate sidewallspacers 240 on each sacrificial gate 231 as well as over eachsource/drain region 212 (or raised source/drain region 213, ifapplicable). A chemical mechanical polishing (CMP) process can then beperformed in order to expose the top surfaces of the sacrificial gates231 and the gate sidewall spacers 240 (see FIGS. 6A-6C). Optionally,before this CMP process is performed to expose the top surfaces of thesacrificial gates 231 and the gate sidewall spacers 240, a CMP processcan be performed to expose the sacrificial caps 232 above thesacrificial gates 231 and the first ILD layer 250 can be recessed. Inthis case, the removed ILD material can be replaced with a material thatis generally the same but with a different density (e.g., a greaterdensity), which is more suitable for use with the CMP process thatexposes the sacrificial gates.

Once the top surfaces of the sacrificial gates 231 and the gate sidewallspacers 240 are exposed, the sacrificial gates 231 can be selectivelyremoved and replaced with replacement metal gates 260 for a pair ofadjacent non-planar FETs 1 and 2 (see FIGS. 7A-7C). Specifically, thesacrificial material of the sacrificial gates 231 can be selectivelyetched over the dielectric materials used for the gate sidewall spacers240 and the first ILD layer 250, thereby creating gate openings in thefirst ILD layer 250. The gate openings will have sidewalls lined withthe gate sidewall spacers 240. Replacement metal gates 260 for eachnon-planar FET can be formed in each gate opening by depositing aconformal high-K gate dielectric layer 261 so as to line the gateopenings and by further depositing one or more metal layers 262 onto thegate dielectric layer 261. Those skilled in the art will recognize thatthe materials and thicknesses of the dielectric and metal layers usedfor the replacement metal gates can be preselected to achieve desiredwork functions given the conductivity type of the FET. In any case,another chemical mechanical polishing (CMP) process can be performed toremove all gate materials from above the top surface of the first ILDlayer 250.

The replacement metal gates 260 and the adjacent gate sidewall spacers240 can then be recessed so that the top surfaces of these features arebelow the level of the top surface of the first ILD layer 250 and sothat vertical surfaces of the first ILD layer 250 are exposed (104, seeFIGS. 8A-8C). Those skilled in the art will recognize that the process104 of recessing the replacement metals and adjacent gate sidewallspacers can include discrete etch processes. For example, a firstselective etch process can be performed to recess the replacement metalgate(s) and a second selective etch process can be performed to recessthe gate sidewall spacer(s).

Next, dielectric spacers 245 can be formed on exposed vertical surfacesof the first ILD layer 250 above each gate sidewall spacer 240 (106, seeFIGS. 9A-9C). That is, a relatively thin conformal dielectric layer(e.g., a silicon oxycarbide layer or other suitable conformal dielectriclayer, as discussed in greater detail below) can be deposited over thepartially completed structure. Then, a directional etch process can beperformed so as to remove the conformal dielectric layer from horizontalsurfaces, thereby leaving dielectric spacers 245 on the exposed verticalsurfaces of the first ILD 250 above the gate sidewall spacers 240,respectively.

After dielectric spacer formation at process 106, dielectric caps 246can be formed on the replacement metal gates 260 such that eachdielectric cap is laterally surrounded by and immediately adjacent to adielectric spacer 245 (108, see FIGS. 10A-10C). Specifically, adielectric cap layer can be deposited so as to fill the spaces aboveeach recessed replacement metal gate 260 and laterally surrounded by thedielectric spacers 245 and a CMP process can be performed, therebyforming the dielectric caps 246 on the replacement metal gates 260. Thedielectric caps 246 can be made of the same dielectric material as thegate sidewall spacers 240. For example, both the dielectric cap 246 andthe gate sidewall spacer 240 could be made of silicon nitride.Alternatively, the dielectric caps 246 and gate sidewall spacers 240could be made of different dielectric materials. For example, the gatesidewall spacers 240 could be made of silicon boron carbon nitride andthe dielectric caps 246 could be made of silicon nitride. In any case,the dielectric caps 246 should be made of a different dielectricmaterial than the dielectric spacers 245 and the first ILD layer 250.

Additionally, recessed metal plugs 248 can be formed in the first ILDlayer 250 on and, particularly, above and immediately adjacent to thesource/drain regions 212 (or, if applicable, above and immediatelyadjacent to the raised first source/drain regions 213, as illustrated)(110, see FIGS. 11A-11C). To form the recessed metal plugs 248 atprocess 110, metal plug openings can be formed (e.g., lithographicallypatterned and etched) through the first ILD layer 250 to thesource/drain regions 212 (or, if applicable, to the raised firstsource/drain regions 213, as illustrated). Then, metal plugs can beformed in the metal plug openings. That is, metal (e.g., a tungsten,cobalt, aluminum or any other suitable metal material) can be depositedinto the metal plug openings and a CMP process can be performed toremove the metal from above the top surfaces of the first ILD layer 250.Additionally, an etch process can be performed to recess the metalwithin the metal plugs openings, thereby forming the recessed metalplugs 248. It should be noted that this etch process can be performed sothat the top surfaces of the recessed metal plugs 248 are level with,lower than, or higher than the top surfaces of the replacement metalgates 260.

To complete the IC structure, both middle of the line (MOL) contacts andback end of the line (BEOL) metal levels can subsequently be formed.Specifically, a stack of dielectric layers 255-256 can be deposited overthe partially completed structure and trenches (e.g., see trenches271-272) for wires and/or vias (not shown) in the first back end of theline (BEOL) metal level (referred to herein as M0) can be formed in anupper portion of the stack (114-116, see FIGS. 12A-12E). Specifically,at process 114, a blanket second interlayer dielectric (ILD) layer 255(e.g., a silicon dioxide layer or other suitable ILD layer) can bedeposited so that it covers the dielectric caps 246 on the replacementmetal gates 260, so that it covers the dielectric spacers 245 on thegate sidewall spacers 240, and so that it fills the spaces within thefirst ILD layer 250 above each recessed metal plug 248. A CMP processcan then be performed to level the top surface of the second ILD layer255 and a hardmask layer 256 (e.g., a titanium nitride hardmask layer orother suitable hardmask layer) can be formed on the second ILD layer255. Then, conventional lithographic patterning and etch processes canbe used to form a pattern of shapes corresponding to the desiredtrenches in the hardmask layer 256 and to then transfer the pattern intothe upper portion of the second ILD layer 255, thereby forming thetrenches 271-272.

Following trench formation at process 116, contact openings, whichextend from the trenches through a lower portion of the stack, can beformed (118, see FIGS. 13A-13C and 14A-14C). Formation of the contactopenings is described in greater detail below and illustrated in theFigures with respect to formation of a first contact opening 281 from afirst trench 271 to one of the replacement metal gates 260 and formationof a second contact opening 286 from a second trench 272 to one of themetal plugs 248. Specifically, a first contact opening 281 can be formedsuch that it extends from a first trench 271 through the lower portionof the stack and through the dielectric cap 246 to a replacement metalgate 260 (119, see FIGS. 13A-13C). For example, a first opticalpolymerization layer (OPL) 280 can be deposited onto the hardmask layer256 and into the trenches 271-272. This first OPL 280 can belithographically patterned with a first contact opening 281 andselective directional etch processes can be performed to extend thefirst contact opening 281 from the first trench 271 through the lowerportion of the second ILD layer 255 to the dielectric cap 246 and thenthrough the dielectric cap 246 to the replacement metal gate 260.Optionally, this first contact opening 281 can land on the replacementmetal gate 260 above an active region (or close thereto), as opposed tobeing aligned above an isolation region. Additionally, a second contactopening 286 can be formed such that it extends from a second trench 272through the lower portion of the stack to a metal plug 248 (120, seeFIGS. 14A-14C). For example, the first OPL 280 can be selectivelyremoved and a second optical polymerization layer (OPL) layer 285 can bedeposited onto the hardmask layer 256 and into the trenches 271-272.This second OPL 285 can be lithographically patterned with a secondcontact opening 286 and a directional etch process can be performed toextend the second contact opening 286 from the second trench 272 throughthe lower portion of the second ILD layer 255 to a metal plug 248. Whileformation of the contact openings is described above and illustrated inthe Figures with respect to formation of a first contact opening from afirst trench to a replacement metal gate and formation of a secondcontact opening from a second trench to a metal plug, it should beunderstood that multiple first contact openings (e.g., to the samereplacement metal gate or to another replacement metal gate) may besimultaneously formed and, similarly, multiple second contact openings(e.g., contact openings to the other metal plugs) may also besimultaneously formed.

After the trenches and contact openings are formed, metal can bedeposited to form BEOL metal wires and/or vias (not shown) in thetrenches and to form contacts in the contact openings (122, see FIGS.15A-15D). The metal deposited at process 122 can be, for example,copper, aluminum or any other metal material suitable for BEOL metallevel wire and/or via formation. Various different techniques fordepositing metal to fill trenches and contacts openings are well knownin the art. Thus, the details of these techniques are omitted from thisspecification in order to allow the reader to focus on the salientaspect of the disclosed methods. Following metal deposition, yet anotherCMP process can be performed to remove metal and the remainingdielectric layer 256 (i.e., the hardmask layer) from above thedielectric layer 255. In any case, the resulting IC structure 200 shownin FIGS. 15A-15D, following metal deposition and CMP, will include atleast: a first contact 293, which is within the first contact opening281 and which extends from a first wire 291 in the first trench 271 toone of the replacement metal gates 260; and a second contact 294, whichis in the second contact opening 281 and which extends from a secondwire 292 in the second trench 272 to one of the metal plugs 248.

In this method embodiment, the dielectric caps 246 on the replacementmetal gates 260, the dielectric spacers 245 laterally surrounding andimmediately adjacent to the dielectric caps 246, and each of thedielectric layers 255, 256 in the stack are specifically made, duringthe various process steps, of different dielectric materials. Forexample, as mentioned above, the dielectric caps 246 on the replacementmetal gates 260 could be made of silicon nitride, the dielectric spacers245 laterally surrounding and immediately adjacent to the dielectriccaps 246 could be made of silicon oxycarbide, the first and second ILDlayers 250 and 255 could be made of silicon oxide and the hardmask layer256 could be made of titanium nitride. Due to these different dielectricmaterials, the widths and lengths of the contact openings 281, 286 arelimited and the contacts 293, 294 formed therein will be self-aligned intwo different dimensions.

More specifically, as shown in FIGS. 13A-13C, the first contact opening281 within the first OPL 280 may have a width (w_(1.1)), as measured ina first direction (e.g., along the X-X′ cross-section) and a length(l_(1.1)), as measured in a second direction (e.g., along the W-W′cross-section) that is perpendicular to the first direction. The width(w_(1.1)) of the first contact opening 281 may be wider than that of thefirst trench 271 such that the first contact opening 281 extends in thefirst direction across opposing sides of the first trench 271 (asillustrated in FIG. 13B). Alternatively, the width (w_(1.1)) of thefirst contact opening 281 may be the same or less than that of the firsttrench 271, but the first contact opening 281 may be misaligned so thatit overlaps one side of the first trench 271 (not shown). Additionally,the length (l_(1.1)) of the first contact opening 281 may be longer thanthe length of the replacement metal gate 260 such that the first contactopening 281 extends in the second direction across the full length ofthe replacement metal gate 260 and over the dielectric spacer 245 (asillustrated in see FIG. 13C). Alternatively, the length (l_(1.1)) of thefirst contact opening 281 may be the same or less than that of thereplacement metal gate 260, but the first contact opening 281 may bemisaligned so that it overlaps the dielectric spacer 245 on one side ofthe replacement metal gate 260 (not shown). However, since thedielectric material of second ILD layer 255 is different from that ofthe hardmask layer 256 and can be selectively and directionally etched,the width (w_(1.2)) of the first contact opening 281, as measured in thefirst direction, within the lower portion of the second ILD layer 255will be no greater than the width of the first trench 271. Furthermore,since the dielectric material of the dielectric cap 246 is differentfrom the dielectric material of the dielectric spacer 245 and the secondILD 255 and can be selectively and directionally etched, the length(l_(1.2)) of the portion of the first contact opening 281 immediatelyabove the replacement metal gate 260 will be no greater than the lengthof the replacement metal gate 260. Thus, the width (w_(1.2)) and length(l_(1.2)) dimensions of the first contact opening 281 are limited and,thus, the resulting contact 293, as shown in FIGS. 15A and 15B, isconsidered self-aligned in these two dimensions. It should be notedthat, optimally, the selective etch process used to etch through thedielectric cap 246 will ensure that etching of the outer edges of thefirst contact opening 281 stops at the level of the dielectric spacer245 (as shown in FIG. 13C). However, even if some etching of the outeredges of the first contact opening 281 occurs, metal plugs 248 arerecessed, as discussed above, so as to avoid any shorting of the firstcontact 293 to the metal plug 248. Similarly, as shown in FIGS. 14A-14C,the second contact opening 286 within the second OPL 285 may have awidth (w_(2.1)), as measured in a first direction (e.g., along the Y-Y′cross-section) and a length (l_(2.1)), as measured in a second direction(e.g., along the Z-Z′ cross-section) that is perpendicular to the firstdirection. The width (w_(2.1)) of the second contact opening 286 may bewider than that of the second trench 272 such that the second contactopening 286 extends in the first direction across opposing sides of thesecond trench 272 (as illustrated in FIG. 14B). Alternatively, the width(w_(2.1)) of the second contact opening 286 may be the same or less thanthat of the second trench 272, but the second contact opening 286 may bemisaligned so that it overlaps one side of the second trench 272 (notshown). Additionally, the length (l_(2.1)) of the second contact opening286 may be longer than the length of the metal plug 248 such that thesecond contact opening 286 extends in the second direction across thefull length of the metal plug 248, over the dielectric spacer 245 andonto the dielectric cap 246 (as illustrated in see FIG. 14C).Alternatively, the length (l_(2.1)) of the second contact opening 286may be the same or less than that of the metal plug 248, but the secondcontact opening 286 may be misaligned so that it overlaps the dielectricspacer 245 and dielectric cap 246 on one side of the metal plug 248 (notshown). However, since the dielectric material of second ILD layer 255is different from that of the hardmask layer 256 and can be selectivelyand directionally etched, the width (w_(2.2)) of the second contactopening 286, as measured in the first direction, within the lowerportion of the second ILD layer 255 will be no greater than the width ofthe second trench. Furthermore, since the dielectric material of thedielectric cap 246 and dielectric sidewall spacer is different from thedielectric material of the second ILD layer 255 and the second ILD 255and can be selectively and directionally etched, the length (l_(2.2)) ofthe portion of the second contact opening 286 immediately above themetal plug 248 will be no greater than the length of the metal plug 248between the adjacent replacement metal gates 260. Thus, the width(w_(2.2)) and length (l_(2.2)) dimensions of the second contact opening286 are limited and the resulting contact 294, as shown in FIGS. 15C and15D, is considered self-aligned in these two dimensions.

The two-dimensional self-alignment of the contacts (i.e., the firstcontact 293 and the second contact 294) effectively eliminates (or atleast significantly reduces) the risk of opens occurring between thewires 291, 292 and/or vias (not shown) in the first BEOL metal level andthose contacts and further eliminates (or at least significantlyreduces) the risk of shorts occurring between the first contact 293 andany metal plugs and between the second contact 294 and the replacementmetal gate 260.

Also disclosed herein are integrated circuit (IC) structures formedaccording to the methods described above. As mentioned above, the ICstructures formed according to the disclosed methods can include, butare not limited to, IC structures that incorporate planar FET(s) ornon-planar FET(s), IC structures that incorporate FET(s) with multiplesemiconductor bodies, IC structures that incorporate FET(s) withconventional gate-first gate(s) or a replacement metal gate(s), etc. Forpurposes of illustration, FIGS. 15A-15D show different cross-sectiondrawings illustrating one exemplary IC structure 200 formed according tothe methods described above. This IC structure 200 has self-aligned MOLcontacts 293-294 to multiple non-planar FET 1 and FET 2 (e.g., finFETs),each FET incorporating multiple semiconductor bodies 210 (e.g., multiplesemiconductor fins) and a corresponding replacement metal gate 260.

Referring to FIGS. 15A-15D, generally each IC structure disclosed hereincan be formed, for example, on a semiconductor-on-insulator (SOI) waferthat includes a semiconductor substrate 202 (e.g., a silicon substrate)and an insulator layer 203 (e.g., a buried oxide (BOX) layer or othersuitable insulator layer on the semiconductor substrate) and asemiconductor layer (e.g., a silicon layer or other suitablesemiconductor layer) on the insulator layer 203 (as shown).Alternatively, each IC structure can be formed on a bulk semiconductorwafer (e.g., a bulk silicon wafer or other suitable bulk semiconductorwafer).

Each IC structure can include at least one field effect transistor (FET)(e.g., see non-planar FET 1 and FET 2). Each of FET 1 and FET 2 canincorporate one or more semiconductor bodies 210. Each semiconductorbody 210 can be, for example, a fin-shaped semiconductor body (i.e., arelatively thing rectangular shaped semiconductor body). Eachsemiconductor body 210 can include at least one channel region 211positioned laterally between source/drain regions 212. For purposes ofillustration, in the IC structure 200 shown in FIGS. 15A-15D, eachsemiconductor body 210 includes two channel regions (one for each of FET1 and FET 2) and further includes a shared source/drain region betweenthe two channel regions. In any case, the channel region(s) 211 can, forexample, be doped with a first dopant so as to have a first conductivityat a relatively low conductivity level.

Each FET can further have a gate 260 (e.g., a conventional gate-firstgate or a replacement metal gate, as shown). For purposes ofillustration, in the IC structure 200 shown in FIGS. 15A-15D, two gates260 are shown (one for each of FET 1 and FET 2) and each gate 260traverses the semiconductor bodies 210 at adjacent channel regions. Agate sidewall spacer 240 can be positioned laterally adjacent to thesidewalls of each gate 260 so as to laterally surround the gate 260. Thegate sidewall spacer 240 can be made of a dielectric material. Thisdielectric material can be, for example, silicon nitride, silicon carbonnitride, silicon boron carbon nitride or any other suitable gatesidewall spacer material. Additionally, a dielectric cap 246 can be onthe top surface of each gate 260. The dielectric cap 246 can be made ofthe same dielectric material as the gate sidewall spacer 240 or adifferent dielectric material. A dielectric spacer 245 can be above thegate sidewall spacer 240 so as to laterally surround and be immediatelyadjacent to the dielectric cap 246. The dielectric spacer 245 can bemade of a different dielectric material than that used for thedielectric cap 246 and gate sidewall spacer 240. Thus, for example, thedielectric spacer 245 may be made of silicon oxycarbide or another othersuitable dielectric material, as discussed in greater detail below.

Optionally, epitaxial semiconductor material (e.g., epitaxial silicon orany other suitable epitaxial semiconductor material) can be on eachsemiconductor body 210 at the source/drain regions 212, thereby creatinga raised first source/drain region 213. For example, as illustrated inFIGS. 15A-15D, the epitaxial semiconductor material can be on the topsurface and opposing sidewalls of each of the semiconductor bodies 210at the source/drain regions 212 (including the source/drain regions thatare shared by FET 1 and FET 2). Optionally, the epitaxial semiconductormaterial on the source/drain regions 212 of adjacent semiconductorbodies 210 can be merged into a single region, as illustrated. In anycase, the source/drain regions 212 and, if applicable, the raisedsource/drain regions 213 can, for example, be doped with a second dopantso as to have a second type conductivity at a relatively highconductivity level.

Each IC structure can further include a first interlayer dielectric(ILD) layer 250 positioned laterally immediately adjacent to each gatesidewall spacer 240 and above the source/drain regions 212 (or, ifapplicable, above the raised source/drain regions 213). The first ILDlayer 250 can be, for example, a silicon oxide layer or a layer of anyother suitable dielectric material that is different from that of thedielectric spacer 245 and dielectric cap 246 adjacent each gate 260.

Recessed metal plugs 248 can be within metal plug openings in the firstILD layer 250 above and immediately adjacent to the source/drain regions212 (or, if applicable, above and immediately adjacent to the raisedsource/drain regions 213, as illustrated). The recessed metal plugs 248may have top surfaces that are at the same level, lower than, or higherthan the top surface of an adjacent gate 260. In any case, the recessedmetal plugs 248 will have top surfaces that are below the level of thetop surface of the dielectric cap 246 on that adjacent gate 260. Thus,each recessed metal plug 248 will be positioned laterally adjacent to agate sidewall spacer 240 opposite a gate 260 and, depending upon theheight of the metal plugs 248, also positioned laterally adjacent to adielectric spacer 245 opposite a dielectric cap 246 (as illustrated).

Each IC structure can further have both middle of the line (MOL)contacts and back end of the line (BEOL) metal levels. That is, at leastone dielectric layer can be above the first ILD layer 250. For example,a second ILD layer 255 can be above the first ILD layer 250. Morespecifically, a second ILD layer 255 can cover the top surfaces of thefirst ILD layer 250, the dielectric cap 246 on each gate 260, and thedielectric spacer 245 on each gate sidewall spacer 240. This second ILDlayer 255 can also fill the recesses above the metal plugs 248 such thatsecond ILD layer 255 covers the top surfaces of the metal plugs 248 andis also positioned laterally adjacent to the dielectric spacer 240opposite each dielectric cap 246. This second ILD layer 255 can, forexample, be the same dielectric material (e.g., silicon oxide) as thefirst ILD layer 250.

Metal wires 291-292 can fill trenches 271-272 that are patterned andetched into an upper portion of the second ILD layer 255. Additionally,contacts 293-294 can extend from the metal wires 291-292 through a lowerportion of the second ILD layer 255. The contacts can include, but arenot limited to, a first contact 293 that extends from a first wire 291through the lower portion of the stack and through one of the dielectriccaps 246 to a gate 260 and a second contact 294 that extends from asecond wire 292 through the lower portion of the stack to a metal plug248. It should be noted that, in the IC structures, the dielectric cap246 on each gate 260, the dielectric spacer 245 that laterally surroundsand is immediately adjacent to a dielectric cap 246, and the dielectriclayers in the stack are all specifically made of different dielectricmaterials such that the first contact 293 and the second contact 294 areeach self-aligned (e.g., in two different dimensions, as discussed ingreater detail above with regard to the method).

In order to avoid clutter in the drawings used to illustrate thedisclosed methods and structures and, particularly, in order toadequately illustrate each of the different types of self-aligned MOLcontacts (i.e., a first contact 293 to a gate 260 and a second contact294 to a meal plug 248) that can be formed according to the disclosedmethods and that can be incorporated into the disclosed structures, onlytwo such contacts 293, 294 are shown in the Figures. However, it shouldbe understood that an IC structure formed according to the disclosedmethods can include multiple instances of the contacts 293, 294 suchthat the gates and source/drain regions of the IC structure arecontacted, as necessary, to ensure proper functioning.

In the methods and structures described above, for an N-type FET, thefirst type conductivity of the channel region(s) can be a P-typeconductivity and the second type conductivity of the source/drainregions can be an N-type conductivity; whereas, for a P-type FET, thefirst type conductivity of the channel region(s) can be an N-typeconductivity and the second type conductivity of the source/drainregions can be a P-type conductivity. Those skilled in the art willrecognize that different dopants can be used to achieve the differentconductivity types and that the dopants may vary depending upon thedifferent semiconductor materials used. For example, a silicon-basedsemiconductor material having N-type conductivity is typically dopedwith an N-type dopant (e.g., a Group V dopant, such as arsenic (As),phosphorous (P) or antimony (Sb)), whereas a silicon-based semiconductormaterial having P-type conductivity is typically doped with a P-typedopant (e.g., a Group III dopant, such as boron (B) or indium (In)).Alternatively, a gallium nitride (GaN)-based semiconductor materialhaving P-type conductivity is typically doped with magnesium (Mg),whereas a gallium nitride (GaN)-based semiconductor material having anN-type conductivity is typically doped with silicon (Si). Those skilledin the art will also recognize that different conductivity levels willdepend upon the relative concentration levels of the dopants.

The methods as described above are used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case, the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

It should be understood that the terminology used herein is for thepurpose of describing the disclosed methods and structures and is notintended to be limiting. For example, as used herein, the singular forms“a”, “an” and “the” are intended to include the plural forms as well,unless the context clearly indicates otherwise. Additionally, as usedherein, the terms “comprises” “comprising”, “includes” and/or“including” specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof. Furthermore, asused herein, terms such as “right”, “left”, “vertical”, “horizontal”,“top”, “bottom”, “upper”, “lower”, “under”, “below”, “underlying”,“over”, “overlying”, “parallel”, “perpendicular”, etc., are intended todescribe relative locations as they are oriented and illustrated in thedrawings (unless otherwise indicated) and terms such as “touching”,“on”, “in direct contact”, “abutting”, “directly adjacent to”, etc., areintended to indicate that at least one element physically contactsanother element (without other elements separating the describedelements). The corresponding structures, materials, acts, andequivalents of all means or step plus function elements in the claimsbelow are intended to include any structure, material, or act forperforming the function in combination with other claimed elements asspecifically claimed.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

Therefore, disclosed above are methods of forming an integrated circuit(IC) structure with self-aligned middle of the line (MOL) contacts to atleast one field effect transistor (FET). In the methods, different,selectively etchable, dielectric materials are used above the gate levelfor at least the following: a dielectric cap above a gate; a dielectricspacer above a gate sidewall spacer and laterally surrounding thedielectric cap; and at least one dielectric layer that covers thedielectric cap, the dielectric spacer, and metal plugs positionedlaterally adjacent to the dielectric spacer and above source/drainregions. Trenches can be formed in an upper portion of the at least onedielectric layer and contact openings can be formed from the trenches tothe gate and the metal plugs. Metal can then be deposited to form wiresand/or vias in the trenches for a first back end of the line (BEOL)metal level and to form contacts, including a gate contact and asource/drain contact, in the contact openings. Due to the differentdielectric materials used above the gate level, the gate andsource/drain contacts will be self-aligned (e.g., in two differentdimensions) to provide protection against the occurrence of opensbetween wires and/or vias in the first BEOL metal level and the variouscontacts and to further provide protection against the occurrence ofshorts between the gate contact and any metal plugs and between thesource/drain contacts and the gate. Also disclosed herein are ICstructures formed according to the methods.

What is claimed is:
 1. A method comprising: forming at least onedielectric layer over a dielectric cap, a dielectric spacer, and metalplugs, wherein the dielectric cap is above and immediately adjacent to agate, wherein a gate sidewall spacer is positioned laterally immediatelyadjacent to the gate, wherein the gate is above a channel region,wherein the channel region is positioned laterally between source/drainregions, wherein the dielectric spacer is above and immediately adjacentto a top surface of the gate sidewall spacer and laterally surrounds andis immediately adjacent to the dielectric cap, and wherein the metalplugs are above the source/drain regions and positioned laterallyadjacent to the gate sidewall spacer and the dielectric spacer that isabove the gate sidewall spacer; forming trenches in an upper portion ofthe at least one dielectric layer; forming contact openings that extendfrom the trenches through a lower portion of the at least one dielectriclayer, the contact openings comprising at least a first contact openingthat extends through the lower portion and the dielectric cap to thegate and a second contact opening that extends through the lower portionto a metal plug; and depositing metal to form wires in the trenches, afirst contact in the first contact opening and a second contact in thesecond contact opening, wherein the dielectric cap, the dielectricspacer, and the at least one dielectric layer comprise differentdielectric materials.
 2. The method of claim 1, the different dielectricmaterials ensuring that the first contact and the second contact areself-aligned.
 3. The method of claim 1, the first contact openinglanding on the gate adjacent to an active region.
 4. The method of claim1, the at least one dielectric layer comprising: an interlayerdielectric layer; and a hardmask layer above the interlayer dielectriclayer, and the different dielectric materials being preselected so thatthe interlayer dielectric layer is selectively etchable against thehardmask layer, the dielectric cap and the dielectric spacer and thedifferent dielectric materials further being preselected so that thedielectric cap is selectively etchable against the interlayer dielectriclayer, the hardmask layer and the dielectric spacer.
 5. The method ofclaim 4, the different dielectric materials comprising titanium nitridefor the hardmask layer, silicon oxide for the interlayer dielectriclayer, silicon nitride for the dielectric cap and silicon oxycarbide forthe dielectric spacer.
 6. The method of claim 1, the gate sidewallspacer and the dielectric cap comprising a same dielectric material. 7.The method of claim 1, the gate sidewall spacer and the dielectric capcomprising two different dielectric materials.
 8. The method of claim 1,the gate and the metal plugs having top surfaces at different levels. 9.A method comprising: planarizing a first interlayer dielectric layer toexpose sacrificial gates and gate sidewall spacers, each sacrificialgate being above channel regions in adjacent semiconductor bodies;replacing the sacrificial gates with replacement metal gates; recessingthe replacement metal gates and the gate sidewall spacers; formingdielectric spacers on exposed vertical surfaces of the first interlayerdielectric layer above the gate sidewall spacers; forming dielectriccaps on the replacement metal gates, each dielectric cap being laterallysurrounded by and immediately adjacent to a dielectric spacer; formingmetal plug openings that extend through the first interlayer dielectriclayer to raised source/drain regions, the raised source/drain regionsbeing positioned laterally adjacent to the gate sidewall spacers andabove source/drain regions that are in the semiconductor bodies onopposing sides of the channel regions; forming metal plugs in the metalplug openings; recessing the metal plugs; forming a stack of dielectriclayers over the dielectric caps, the dielectric spacers, and the metalplugs, the stack comprising a second interlayer dielectric layer and ahardmask layer on the second interlayer dielectric layer; formingtrenches in an upper portion of the stack; forming contact openings thatextend from the trenches through a lower portion of the stack, thecontact openings comprising at least a first contact opening thatextends through the lower portion and a dielectric cap to a replacementmetal gate and a second contact opening that extends through the lowerportion to a metal plug; and depositing metal to form wires in thetrenches, a first contact in the first contact opening and a secondcontact in the second contact opening, wherein the dielectric caps, thedielectric spacers, and each of the dielectric layers in the stackcomprise different dielectric materials.
 10. The method of claim 9, thedifferent dielectric materials ensuring that the first contact and thesecond contact are self-aligned in two dimensions.
 11. The method ofclaim 9, the first contact opening landing on the replacement metal gateadjacent to an active region.
 12. The method of claim 9, the differentdielectric materials being preselected so that the second interlayerdielectric layer is selectively etchable against the hardmask layer, thedielectric caps and the dielectric spacers, and the different dielectricmaterials further being preselected so that the dielectric caps areselectively etchable against the second interlayer dielectric layer, thehardmask layer and the dielectric spacers.
 13. The method of claim 9,the different dielectric materials comprising titanium nitride for thehardmask layer, silicon oxide for the second interlayer dielectriclayer, silicon nitride for the dielectric caps and silicon oxycarbidefor the dielectric spacers.
 14. The method of claim 9, the gate sidewallspacers and the dielectric caps comprising a same dielectric material.15. The method of claim 9, the gate sidewall spacers and the dielectriccaps comprising two different dielectric materials.
 16. The method ofclaim 9, the recessing being performed such that the replacement metalgates and the metal plugs having top surfaces at different levels.
 17. Amethod comprising: forming at least one dielectric layer over adielectric cap, a dielectric spacer, and metal plugs, wherein thedielectric cap is above a gate, wherein the gate has gate sidewallspacers and is adjacent to a channel region, wherein the channel regionis positioned laterally between source/drain regions, wherein thedielectric spacer is above the gate sidewall spacer and laterallysurrounds and is immediately adjacent to the dielectric cap, and whereinthe metal plugs are above the source/drain regions and positionedlaterally adjacent to the dielectric spacer; forming trenches in anupper portion of the at least one dielectric layer; forming contactopenings that extend from the trenches through a lower portion of the atleast one dielectric layer, the contact openings comprising at least afirst contact opening that extends through the lower portion and thedielectric cap to the gate and a second contact opening that extendsthrough the lower portion to a metal plug; and depositing metal to formwires in the trenches, a first contact in the first contact opening anda second contact in the second contact opening, wherein the at least onedielectric layer comprises: an interlayer dielectric layer; and ahardmask layer above the interlayer dielectric layer, and wherein thehardmask layer, the interlayer dielectric layer, the dielectric cap andthe dielectric spacer comprise different dielectric materials, andwherein the different dielectric materials comprise titanium nitride forthe hardmask layer, silicon oxide for the interlayer dielectric layer,silicon nitride for the dielectric cap and silicon oxycarbide for thedielectric spacer.
 18. The method of claim 17, the different dielectricmaterials ensuring that the first contact and the second contact areself-aligned.
 19. The method of claim 17, the first contact openinglanding on the gate adjacent to an active region.
 20. The method ofclaim 17, the different dielectric materials being preselected so thatthe interlayer dielectric layer is selectively etchable against thehardmask layer, the dielectric cap and the dielectric spacer, and thedifferent dielectric materials further being preselected so that thedielectric cap is selectively etchable against the interlayer dielectriclayer, the hardmask layer and the dielectric spacer.